In the design of electric vehicles, high power semiconductors are frequently used for motor control. These high power semiconductors include switching devices such as IGBT's (integrated gate bipolar transistors) or FET's (field effect transistors). During the normal operation of an electric vehicle, between 500.about.1000 watts of heat is generated. This heat must be removed from the semiconductors in order to prevent damages to the semiconductors from occuring and to allow them to function properly.
Typically, a natural convection heat sink is used in automobiles to remove heat generated by semiconductors. However, it has been found that in the case of an electric vehicle, standard natural convection and even forced convection heat sinks are inadequate. For instance, one electric vehicle application uses a forced convection heat sink by utilizing several muffin fans for increased air flow. Even with this arrangement, full motor drive is time limited due to the excessive heat generated by the semiconductors. Moreover, besides the disadvantage of having to use a very large heat sink and muffin fans, the vehicle efficiency suffers due to the running fans and the additional weight as indicative by the miles achieved per battery charge.
Others have also proposed solutions for the semiconductor heating problem, for instance, the use of liquid cooled coldplates. However, the use of liquid cooled coldplates generates other problems such as the requirements of maintaining a liquid flow, piping, a reservoir and a liquid-to-air heat exchanger (i.e. a radiator). These additional equipment not only adds complexity to the cooling system, but also adds costs, weight and thus decrease the vehicle operating efficiency. For instance, U.S. Pat. No. 3,965,971 issued to Roggencamp discloses a cooling system for semiconductors, specifically, silicon controlled rectifiers. The rectifiers are liquid cooled by a closed circuit cooling system utilizing an osculating pump, a heat exchanging reservoir, and a rectifier mounting block. The rectifier mounting block forms a fluid chamber for ease of heat exchange. The Roggencamp device therefore required large equipment expenses and complex equipment setup.
It is therefor an object of the present invention to provide a device for dissipating heat from high power semiconductors in an electric vehicle that does not have the drawbacks of the prior art methods.
It is another object of the present invention to provide a device for dissipating heat from high power semiconductors in an electric vehicle by using a convoluted fin heat exchanger.
It is a further object of the present invention to provide a device for dissipating heat from high power semiconductors in an electric vehicle by using a convoluted fin heat exchanger and high volume ram air.
It is yet another object of the present invention to provide a device for dissipating heat from high power semiconductors in an electric vehicle by using a convoluted fin heat exchanger and a minimum air flow of 30 CFM.
It is still another object of the present invention to provide a device for dissipating heat from high power semiconductors in an electric vehicle by using a convoluted fin heat exchanger equipped with a funnel-shaped opening for the intake of large volume ram air.